1. Field of the Invention
The present invention relates to an image forming apparatus and an image forming method in the image forming apparatus, and more particularly, to an image forming apparatus and an image forming method for performing a printing by controlling each unit of an engine.
2. Description of the Related Art
A general image forming apparatus such as a printer and a multifunction product (MFP) includes a controlling unit that develops printing data into drawing data in accordance with an instruction to execute printing received from an operation panel or a personal computer (PC) or the like connected to a communication network, and an engine that controls a photosensitive body, a charging unit, an optical writing unit, a developing unit, a separating unit, a cleaning unit, and the like to print the drawing data developed by the controlling unit on a sheet.
For example, upon receiving the drawing data from the controller, the engine charges the photosensitive body, and then operates the optical writing unit to form an electrostatic latent image on the photosensitive body. Thereafter, the engine transcribes a toner image on a sheet fed by a paper feeding unit. The engine heats and pressurizes the sheet on which the toner image is transcribed, and fixes the toner image on the sheet. Printing is completed by performing a series of the processing (Japanese Patent Application Laid-open No. 2002-49202).
FIG. 14 is a timing chart for explaining the processes of activating the units of the engine, such as the charging unit, the developing unit, the transcribing unit, the separating unit, and the cleaning unit, then executing printing, and terminating the printing when the engine has received drawing data from the controller in the conventional image forming apparatus.
As shown in FIG. 14, in the conventional image forming apparatus, when a print start instruction is received from the controller, the engine is activated (P1), the charging unit, the developing unit, and the transcribing unit are activated, and then the separating unit is activated. After completing the activation of the separating unit, the activation of the engine is completed (P2). The period from P1 to P2 is called a process activation period Ta in FIG. 14.
After completing the activation of each unit, the engine performs a series of the processing for printing the drawing data received from the controller such as light exposure for forming an electrostatic latent image, development for forming a toner image by supplying a toner from the developing unit to the electrostatic latent image on the photosensitive body, transcription for transcribing the toner image on the photosensitive body onto a sheet by a transcription voltage of the transcribing unit, and separation for separating the sheet on which the toner image is transcribed from the photosensitive body by a separation voltage of the separating unit (process printing period Tb).
After a predetermined period of time in the process printing period Tb, the engine confirms whether an instruction to start printing a next page is sent from the controller, and when no instruction is sent to start printing in a predetermined period of time, terminates the charging unit (P3). Thereafter, similarly to the activation of each unit of the engine, the developing unit, the transcribing unit, and the separating unit are terminated, and the cleaning unit is actuated. When the cleaning unit ends the operation, termination of each unit of the engine ends (P4). The period from P3 to P4 is called a process termination period Tc in FIG. 14.
As can be seen, in the image forming apparatus, each unit of the engine is terminated when no instruction to start printing a next page is sent during printing (Tb). This is because when no instruction to start printing is sent in a predetermined period of time, the engine determines that printing has been completed or an abnormality has occurred and attempts to end the printing.
Drawing data may have a large data amount, or include several pages with high image quality, therefore, it takes a long time for the controller to develop the printing data of the pages into the drawing data, thereby preventing the controller from instructing print start in a predetermined period of time. In such a case, an instruction to start printing a next page is received after starting termination of each unit of the engine in the conventional image forming apparatus as shown in FIG. 15. The charging unit, the developing unit, and the like can be activated only after all of the charging unit, the developing unit, and the like are terminated. The time for printing becomes unnecessarily long, and due to reactivation of the units of the engine, the units are degraded more, and thus the service life of the image forming apparatus is shortened.